Synthesis of hydrocarbons



W. G. SCHARMANN Filed Dec. 28, 1945 SYNTHESIS OF H'YDROCARBONS ClbbowneqPatented Nov. 21,

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ssa.m SYN'I'IIESIS F IIYDBOCARBONS Walter G. Schannarur, Weetileld, N..I., aseignor te Stnlldnnl 0ll Devolo poratlon o! Delaware runent 00111Applicatlon December 28, 1945, 80111.! Nu. 687,893 3 China. (Cl.260-449..)

of the catalytic conversion oi' carborinonoxide with hydrogen to formhydrocarbons having more than one carbon atom per molecule andoxygenated products.

'I'he synthetic production of liquid hydrocarbons i'rom gas mixturescontaining various proportions of carbon monoxide and hydrogen isalready known and numerous cataiysts, usually containing an iron groupmetal, have been described which are specificaliy active in promotingthe desired reactions at certain prei'erred operating conditions. Forexample, cobait supporbed on an inert carrier is used when relativelylow pressures (atmospheric to 5 atmospheres) and low temperatures (375to 425 F.) are applied in the manufacture of a substantially saturatedhydrocarbon product while at the higher temperatures (450 to 750 F.) andhigher pressures (5 to 25 atmospheres and higher) required i'or theproduction of unsaturated and branched-chain products of high antiknockvalue, iron-base catalysts are more suitable. In both cases the activityof the catalyst declines steadily during the course of the reactionchiefiy due tothe deposition of nou-volatile conversion products, suchas carbon, parafiin wax and the like, on the cataiyst, as well as due toa change in the degree of oxidation of the active component Variousmethods of preventing these changes in catalyst characteristics or forrestoring lost activity to the catalyst have been proposed, includingcontinuous or intermittent extraction of the catalyst in-situ withsuitable solvents, intermittent in-situ treatment of the catalyst wihhydrogen end/or steam at the conversion temperature or highertemperatures or continuous hydrogen treatment of powdered catalystcontinuously circulated trom and to the conversion zone through asuitable regeneration zone, ap- Plyin the tluid catalyst technique. Ithas also been proposed to subject the cataiyst, particularly cobaitcatalysts, prior to the wax removal with the aid oi' hydrosen at hightemperatures, to an oxidizing treatment with oxygen, steam or carbondioxide at elevated temperatures in order to cause a superiicialoxidation of the catalyst metal.

A11 these methods contempiate the removal of paraflin wax and sirniiarhigh-moiecuiar hydrocarbon products trom the catalyst; the operateeihciently whenev'er and to the extcnt in which catalyst deactivation isdue to the deposition oi' such high-molecular hydrocarbon products.However, the deactivation oi iron catalysts has been tound to difler inthis respect considerably trom that of cobalt catalysts. 'Ihe letter isdue essentialiy to the deposition of paraflin wax and may be overcome bya suitable reduction of the parai'lin deposit by conventional methods.'Ihe deactivation of iron catalysts, on the other hand, appears to becaused to a substantial extent by the deposition of coke-like materialiormed by the dissociation and cracking oi' carbon mono:- ide andunstabie hydrocarbons, which taire place at the higher temperatures andpressures associated with the use of iron-base catalysts. De posits ofthis type cannot be efliciently removed or prevented by the knownreactivation methods and, i! allowed to accumulate excessively. alzoadversely affect these characteristics of the catalyst which determineit's utility as a fluidizable solid in processes employing the so-calledfluid solids technique in which the reactants are contacted with a denseturbuleritbed of flnely-divided catalyst fiudized by the gaseousreactants and reaction products. It is also probable that changes of thedegree of oxidation of the iron component cause changes in iron catalystactivity. My invention relates to an improved reconditioning processwhich permits the rem0val of catalyst deposits to a desired degree andthe reactivation of catalysts, particularly iron catalysts used in theSynthesis of hydrocarbons trom carbon monoxide and hydrogen.

It is, therefore, the main object of my invention to reconditioncatalysts which have been reduced in activity and utility in thecatalytic production of hydrocarbons end/or oxygenated products tromcarbon oxides and hydrogen.

It is a further object of my invention to recondition catalysts of thetype specifled which cannot be reactivated by conventionaimethods ofreactivation.

It is also an object of my invention to reactivate catalysts of the typespecified which have been rduced in activity and/or utility by depositsincluding substances other than paramn wax.

A more particular object 01' my invention is to reactivate catalystswhich have been reduccd in activity in the catalytic hightemperaturehigh pressure conversion of carbon monoxide with hydrogen.

A still more speciflc object of my invention is 3 the reoonditioning ofiron-base catalvsts which have been reduced in activlty and/or utilityin the last-mentloned process.

It is also an important object of my invention to provide a proces inwhich the catalysts of the types mentioned are continuously orlntermittently wlthdrawn trom the converslon zone, reconditloned andreturned to the conversion zone without interference with a continuousoperation of the conversion process.

ther objects of my lnvention will appear hereinafter.

The characteristicsand conditions oi! the conventlonal methods forreactivating hydrocarbon synthesis catalysts are determlned by thedesire to recover substantially unchanged the highly valuable paraflinwaxdeposlted on the deactivated catalyst. I have i'ound that thedeposits which deactivate iron-base catalysts contain preponderatingproportions of practically worthless ooke-like materials and only verylittle. 1! any, valuable compounds, such as paraiiin wax, whose 10ss orrecovery does not appreciably aii'ect the economie balance of thesynthesis process.

I achieve, theretore, conslderable improvements in the reconditioning ofsynthesis catalysts by subjecting synthesis cataysts oi.' reducedutility particularly iron-base catal-sts irom the high temperature-highpressure synthesis, to a tr eatment with an oxidlzing gas. such as airand/or oxygen, followed by a reduction with hydrogen or another reducinggas, such as the gas mixture used for the synthesis reactlon orsynthesis tail gas. In the oxidizing sten. the amount of deactivatlngdeposits which form volatile oxidation products, such as coke, tar,resins, parafiln wax.

suli'ur comounds, etc. is reduced to a deslred exterit by oxidation orcombustion to form mainly carbon oxides and small amounts of water. Atemperature range of trom 900 to 1500 F. has

been i'ound most sultable tor this step of my process. The oxidationtreatment may even be carried to a point at which oxidation of the metalcomponents of the catalyst takes place. The catalyst subjected to theoxidi ing treatment is thereafter subjected to treatment with redncinggases at temperatures ranging from 800 to 1400 F. whereby the activitvof the catal.vst is substantialy restored. I prefer to conduct bvtwestage reconditioning process in a continuous manner in cooperationwith a continuously operated synthesis process, applving the principlesand conditions of the fluid solids technique, as will appear moreclearly hereinaiter.

The accompanyine drawing which forms a part of the instant specificationand whlch is to be read in conjunction therewith is a diagrammatic viewof one form of apparatus capable oi' carrying out the process of myinvention. More particularly rei'erring now to the drawing, synthesis reactor l contains finely-divided iron-bas synthesis cataiyst of anysuitable composition known in the art of the hydrocarbon synthesis andhaving a particle size of from 100 to 400 mesh, preferably about 200mesh. The synthesis gas mixture from any source indicated generally at2, having a molar ratio of hydrogen. to carbon monoxide varying betweenthe approximate limits 01' -311, is i'ed by compressor 3 through line 4to the catalyst zone of reactor I and enters the letter through adistribution plate 5 at a velocity controlled within the limits of fromto ft. per second so as to maintain the catalyst in a form of a dense.highly turbulent, fluidized mass having a.

fluidized catalyst in the catalyst zone below the level L1 may have adensity of 15 to 100 lbs. per cu. ft. while the catalyst density abovethe level L1 may be as low as 0.05 1b. per cu. tt. The catalystparticles reaching the disengaging zone are separated trom the reactedgas in separator 6 which may be a centrifugal or electric typeseparator, and the gas treed of catalyst leaves reactor l through line 1and is passed through line 8 to a conventional recovery system 8. Aportion of the gas leaving reactor l through line "I may be recycledelther at or about the reactor outlet temperature or at lowertemperature through line 9 to lin 4 andto the reaction zone in order toassist in the fluidization of the catalyst and/or the temperaturecontrol of the reaction zone. As a result of the excellent heattransfercharacteristics of the fluidized catalyst mass contained within reactorI, the reaction temperature may be easily kept constant within a fewdegrees F. at the desired temperature level which for the case ofiron-base catalysts lies between the approximate limits of 450 and 800F. preferably between 500 and 650 F. Surplus heat of the exothermicreaction may be withdrawn, and heat required for startlng up theproccess may be supplied by any conventional means (not shown).

To maintain the activity of the catalyst at a high level, fluidizedcatalyst is withdrawn trom reactor I at a point above distribution plate5 through line I0 which may have the form of a standpipe whose contentsexert a pseudo-hydrostatic pressure on the base of pipe I0 leading intoline H wherein the catalyst is mixecl with a carrier gas, preferably anoxidizing gas such as air or air enrichecl with oxygen supplied by pumpI I from line l3; steam or an inert fluidization gas may be added fromline 22' to obtain the desired degree of fiuidization. The gas in line II may be preheated to any desired temperature between the approximatelimits of 7001200 F. The catalyst suspended in the carrier gas is passedtrom line H into oxidation reactor I2 which is similar in constructlonto synthesis reactor I. havng a distribution plate 12' and a gas-solidsseparator I 4. The catalyst within oxidation reactor I2 forms under theaction of the gas supplied through line II and the combustion gasesformed, a dense, hghly turbulent, fluidized mess similar to thatinreactor I forming an upper level L12. The oxidizing portion of the gasessup plied through line II is so controlled as to cause the desiredcombustion of the carbonaceous deposits on the catalyst at temperatureswhich may vary between about 1000 and 2000" F. Combustion gases leavereactor l2 through separator H and line I8 to be used in the system asfluidizing gas or, as shown below, for heat recovery or to be dlsposedof as desired; they may also be passed to en additional catalystseparation zone (nut shown) to recover any catalyst fines carried by the(zombustion gases.

In most cases the amount of carbonaceous dewell-deflned upper level L1,which is determined P 511 0111 h ly t 1S ufli l y l r e 8 erate moreheat by combustion of the amonnt ot carbon to be removed than isrequired to main- .tain oxidation reactor |2 at the desired temperature.In order to prevent undesired overheating in these cases. I provide iora catalyst circulation trom reactor I2 downwardly through line II to acooler 24 and trom there through line 21 back to reactor I2. Apreierably inert carrier gas such as steam. flue gas. etc., isintroduced through line 22 into line 2! to carry a dilute suspension ofcooled catalyst upwardly to reactor I2. It will be understood that thetemperatures of cooler 20 and the amount of catalyst passed therethroughmay be readily controlled so as to maintain any desird constantcombustion temperature in reactor I2. If the amount of carbonaceouscatalyst deposit is insuflicient to generate the heat required inreactor l2, a combustible gas such as natural gas, synthesis feed ortail gas, or the like, may be supplied to reactor |2 through line I4' togenerate additional heat oi combustion.

After the desired amount of carbonaceous anam deposit has been removedtrom the catalyst in oxidation reactor I2, the fluidized catalyst iswithdrawn downwardly through line 23 and passed through a stripping zoneI5 wherein any oxidizing gas adhering to the catalyst may-he removed byan inert stripping gas such as steam, flue gas,

etc. supplied trom line 22. Ii desired, the stripping treatment may beso controlld as to ieave sumcient oxidizing gas on the catalyst to causea limited amount of combustion to take place with the H2 in reductionreactor 28, as will appear more clearly hereinaiter.

The catalystleaving stripping zone Il through line 23 istaken up by areducing gas, such as hydr0gen synthesis feed or tail gas, which i'iowsthrough line 24 and which is preheated to a temperature of about 1000 to1600? F. in heater 25. Het flue gas trom reactor |2 may be passedthrough line 28 substantiaily at the temperature of reactor l2 to supplyheat to the hydrogen in line 24. The suspension of catalyst and hydrogenformed in line 24 is passed under the action of compressor 2'| into thereduction reactor which is of a construction similar to that of reactorsi and I2. H desired. line 23 in combination with stripping zone l5 andline 23' may be designed to serve as a standpipe whose fluidizedcontents exert a pseudo-hydrostatic pressure on the base of line 23'which aids in the transport of the suspension oi' catalyst in reducinggas to the reduction reactor 20. Reactor 20 is provided with adistribution plate 29 and a gas-solids separator 30. The catalyst inreactor 20 forms again a dense, highly turbulent, fluidized mass havinga well-deflned leve! Iea and is mainained at the desired reductiontemperature which may vary within the approximate iimits of 800 to1400 1. Gaseous products, such as steam and unconsumed hydrogen, leavereactor 28 through line ll which leads intoa cooler 32 wherein water andany catalyst fines which were not separated in separator arerespectively condensed and precipitated and withdrawn through line 33ter further catalyst recovery, if desired. Surplus hydrogen is remcvedoverhead from cooler 32 through line 24 and either discarded throughline I5or recycled through line 36 to compressor 21 and hydrogen i'eedline 24. Fresh hydrogen may b added through line 31 to hydrogen recycleline 30. Synthesis ieed or tail gas may be added trom lines 33 and 35,respectively. While in most cases the senslbie heat of the hot cataiystwithdrawn gen preheat is suiiicient to maintain reactor 23 at thedesired reduction temperature, additional heat may be generated by thecombustion of small amounts of H2 with the aid of an oxldizin: na suchas air and/or oxygen supplied through line 24' or adhering to thecatalyst trom reactor I2. If air is used ior this purpose, the hydrogenrecycle must be purged through line 35 to prevent accumulation of inertgases in the system.

Catalyst adjusted to the desired carbon content and degree of oxidationis withdrawn trom the bottom.oif reduction reactor 23 through line 40and passed through a stripping zone 4l wherein. it desired, adheringgases may be removed by a stripping gas such as steam. natura1 gas,synthesis feed 01' tail gas, etc. supplied through line 42 trom lines39', 42 er 43. Reconditioned catalyst leaves stripping zone 41 throughline 44 which may, simiiar to lines "1 and 23, be designed as astandpipe tc exert a pseudo-hydrostatic pressure on the base of line 44.The catalilst in line 44 may thus be fed under its own pseudohydrostaticpressure into synthesis gas feed line 4 and thus retumed to thesynthesis reactor i as a suspension of eatalyst in synthesis gas.Preferably, line 44 is provided with a cooler 40 in order to lower thetemperature of the reduced catalyst to be recycled sufiiciently belowsynthesis temperature, say to a temparature between the approximatelimits of 100 to 400 R. in order to prevent premature reaction outsidesynthesis reactor I.

It shouid be understood that the reconditioning system, comprisingessentially reactors i2 and 20, may be conveniently operated under thesame pressure as synthesis reactor I However. 11' desired. either higheror lower pressures may be applied in the reconditioning system, usingsuch means well known in the fluid solids technique as pressurized ordepressurized catalyst ieed hoppers.

In order to further illustrate my invention, the following example isgiven which should not be construed as limiting the same in any mannerwhatsoever.

Example Reactor I is operated at a dense phase capacity of about 10 cu.ft. containing about 500 lbs. of iron catalyst havng an oxygen.contentof about 10% and a carbon content of about 20% in a fluidized catalystphase of about 50 lbs. per cu. ft. density which is contacted by about10,000 cu. ft. per hour of fresh synthesis gas containing 31.5% C0 at atemperature of about 600 F. and a pressure of about 15 atmospheres. Atthese conditions, about 1.5% of the C0 in the fresh gas is decomposed toform carbon deposited on the catalyst at a rate of about 1.5 lbs. perhour, whiie the oxygen content of the catalyst is increased by about 0.21b. per hour.

In order to maintain these operating conditiens, about 25 lbs. ofcatalyst per hour is cir- |2 and about 220-230 cu. ft. of air per houris supplied to reactor I2. T0 maintain a combustien temperature of about1000 F., about 400-450 lbs. of catalyst per hour is recycied throughlines I9 and 2! through cooler 20 wherein the recycle catalyst stream isadjusted to a temperature of about 800 F. Catalyst containing about '15%of carbon is withdrawn through line 23 at the rate of about 23-241bs.per hour, passed to reac fl'0m reactor II in ccxnbination with thehydro- 7 tor 28, subiccted th n 1 m l lw 8 r i 7 ment at about 800 I".in which ebout 4-5 on. it. per hour of l-h at normal conditions isconsumed. The reconditioned catalyst is returned to reactor i at atemperature of about 400 I'.

It should be understood that the rate at which the catalyst iscirculated through the reconditioning system depends main1y on theamount of carbon to be removed per unit of catalyst and time. 'I'hus, atthe conditions outlined in the example, if the carbon content is to bereduced trom 20% to about 0.5%, about 30-40% of the catalyst charge iscirculated per day through the reconditioning system. 'I'i1is flgurerises to about Gil-70% if the carbon content is to be reduced from 20%to about 10% and may exceed 100% at the conditions of the example. Ingeneral, the catalyst circulation rate falls within the 'approximatelimits of 1 and 100% per day of the cata- 1yst charge of reactor i.

The process of the present invention may be widely varied; fr instance,the system described above may be readily adapted to the use ofsynthesis catalysts other than iron-base catalysts, such as cobait orother group VIII metal-base catalysts, by appropriate variations of thetemperature and pressure in the synthesis reactor and adaptation of theoxidizing and reducing conditions in reactors 12 and 20, respectively,to the speciflc composition and propertiesof the catalyst depositsformed in these modiflcations of the synthesis reaction. Activators,such as alkaline earth and rare earth metal oxides may be added to thecatalysts which may be supported of inert carrier materials, such askieselguhr, silica gel, and the like. The reconditioning of the catalystmay also be conducted intermittently rather than continuousiy in fulladaptation to the rxte of deactiva;tion of the catalyst. Spent cataiystmay be withdrawn from the system through line 99 and fresh make-upcatalyst may 10001600 I"'. sufliciently high t0 initiate and maintainthe combustion of oombustible catalyst deposits, removing at least asubstantial portion of carbonaceous deposits from the catalyst bycombustion in the course of said oxidizing treatment, passing catalystsubstantially at said temperature trom said oxidation zone to a.reduction zone, wherein it is maintained in the form of a densefiuidized bed, subjeoting the catalyst in said reduction zone to areducing treatment with a reducing gas at a temperature of about800-1400 F. but not higher than said first mentoned temperature, addingsufiicient oxidizing gas to said reduction zone to generate by a limitedcombustion of said reducing gas suflicient heat to mantain said secondnamed temperature in said reduction zone, and returning reduced catalystto said conversion zone.

2. The process as clamed in claim 1 in which the conversion is carriedout at a. temperature wthin the approximate range of 450 to 800" F.

be i'ed from hopper 50 through lines 52 and/or 54 to reactor 1, or atany desired point to the reconditioning system, for example through line159 into line 26. Pipes I0, I9, 23, 00, 52, 54 and E59 may be aerated ina manner known per se to facilitate the downward flow of solids. Theseand other changes may be made in the details disclosed in the foregoingspeciflcation without departure from the inventlon or sacriflcing theaclvantages thereoi.

The process of the present inventlon is not to be limited by any theoryor mode of operation but only by the following claims.

1. In the continuous production of hydrocarbons by conversion of carbonoxides with hydrogen in the presence of a finely dvided iron-basecatalyst maintained in a conversion zone in the form 01' a dense,fluidized mass in which used fluidized catalyst is withdrawn from theconversion zone, reactivated in a regeheration zone in the form of adense, fluidized mass and thereaiter and a pressure wthin theapproximate range of 5 to 50 atmospheres, and said deposits comprisecoke-lke materials.

3. The process of claim 1 in which the reduced catalyst is cooled to atemperature be1ow that of said converson prior to its return to saidconverson zone.

WALTER G. SCHARMANN.

REFERENCES CIIED The following references are of record in the file ofthis patent:

UNI'IED STATES PATENTS Number Name Date 2,289731 Roeien July 14, 19422.325,516 Holt et al July 27, 1943 2,348,418 Roesch et al May 9, 19442,360787 Murphree et al Oct. 17, 1944 2365,094 Michael et al Dec. 12,1944 2,366372 Voorhees Jan. 2, 1945 2,386,491 'Mc0mie Oct. 9, 19452391,334 Nicholson Dec. 18, 1945 2.393,909 Johnson Jan. 29, 19462,455,419 Johnson Dec. 7, 1949 FOREIGN PATENTS Number Country Date557,904 Great Britain Dec. 10, 1943

1. IN THE CONTINUOUS PRODUCTION OF HYDROCARBONS BY CONVERSION OF CARBONOXIDES WITH HYDROGEN IN THE PRESENCE OF A FINELY DIVIDED IRON-BASECATALYST MAINTAINED IN A CONVERSION ZONE IN THE FORM OF A DENSE,FLUIDIZED MASS IN WHICH USED FLUIDIZED CATALYST IS WITHDRAWN FROM THECONVERSION ZONE, REACTIVATED IN A REGENERATION ZONE IN THE FORM OF ADENSE, FLUIDIZED MASS AND THEREAFTER RETURNED TO THE CONVERSION ZONE,THE IMPROVEMENT WHICH COMPRISES CONTINUOUSLY HEATING THE WITHDRAWNCATALYST BY THE COMBUSTION OF AN EXTRANEOUS COMBUSTIBLE GAS WITH FREEOXYGEN IN CONTACT WITH THE CATALYST TO A TEMPERATURE SUFFICIENTLY HIGHTO INITIATE AND MAINTAIN THE COMBUSTION OF COMBUSTIBLE CATALYSTDEPOSITS, SUBJECTING THE HEATED CATALYST TO AN OXIDIZING TREATMENT WITHAN OXIDIZING GAS IN AN OXIDATION ZONE WHEREIN THE CATALYST IS MAINTAINEDIN THE FORM OF A DENSE FLUIDIZED MASS AT A TEMPERATURE OF ABOUT1000*-1600*F. SUFFICIENTLY HIGH TO INITIATE AND MAINTAIN THE COMBUSTIONOF COMBUSTIBLE CATALYST DEPOSITS, REMOVING AT LEAST A SUBSTANTIALPORTION OF CARBONACEOUS DEPOSITS FROM THE CATALYST BY COMBUSTION IN THECOURSE OF SAID OXIDIZING TREATMENT, PASSING CATALYST SUBSTANTIALLY ATSAID TEMPERATURE FROM SAID OXIDATION ZONE TO A REDUCTION